This research will examine relationships among pain, depression, and functional limitations among older persons with osteoarthritis. The most common source of pain and functional limitations in later life, osteoarthritis (OA) affects at least half and perhaps as many as 90% of all persons aged 65 and over. Although chronic illness and its accompanying pain and disability are known to be associated with depression in late life, there has been surprisingly little research addressing the affective consequences of osteoarthritis. This research will therefore integrate knowledge from the literatures on chronic illness and disability in general, pain, arthritis, and depression to test a longitudinal model of interrelationships among severity of OA, its immediate manifestation in pain and functional limitations, and consequent effects on emotional state. Specific aims are: 1) to document the extent of depression among older persons with symptomatic OA of the knee; 2) to explicate cross-sectional associations among objective severity of osteoarthritis, pain, functional limitations, and depression; 3) to examine how personal characteristics and coping strategies moderate associations among disease severity, functional limitations, pain, and depression as a function of perceived control vs. helplessness regard disease effects, and 4) to test a longitudinal model of covariation among experienced pain, depression, and functional limitations as a "downward spiral" in which the three variables feed one another over time. These aims will be achieved in a 4-year longitudinal study of 400 older persons with OA of the knee. On entering the study, respondents will have undergone extensive examination to determine the objective severity of osteoarthritic changes. They will also complete self-report measures of pain, functional limitations, depression, coping strategies, and demographic and other personal characteristics. Baseline data will reveal cross-sectional interrelationships among general health, severity of OA, pain, functional limitations, and depressed mood, as well as moderating influences of personal characteristics on those interrelationships. Two yearly follow-up interviews will identify predictors of change in pain, functional limitations and depression, and elucidate the likely causal ordering of changes in those variables among elderly OA patients.